80-column card firmware

[Robert Jensen <bob_jensen@jhuapl.edu>]

I have a videx-like 80-column card (not Videx, but advertised
as completely compatible) and it appears to have 3 2K EPROM
chips on it. I base this on the chip sizes and the apparent
existence of a UV erasing window beneath the label on all three.

2K of memory get mapped into the $c800-$cfff range to run
the thing. Another 256 bytes get mapped into $c300-$c3ff (for
slot 3).

Why does this thing appear to have 6K of firmware? If it really
has that much, how does the system reach it all? Is it bank
selected? Is it really something else? The 8 pages of typed
docs that came with the thing years ago don't give a clue.

I want to modify the firmware to solve a problem that I have
not solved in a less intrusive fashion. I know what I want to
change, I just don't know which EPROM to replace. Without
other information, I will pull all three and dump their
contents. I am hoping that someone can save me the trouble.
=========================================================
Bob Jensen
bob_jensen@jhuapl.edu